feat: add API key caching via settings.json (#16)

Co-authored-by: Letta <noreply@letta.com>

src/agent/modify.ts

@@ -20,7 +20,7 @@ export async function updateAgentLLMConfig(
   modelHandle: string,
   updateArgs?: Record<string, unknown>,
 ): Promise<Letta.LlmConfig> {
-  const client = getClient();
+  const client = await getClient();
 
   // Step 1: Update model (top-level field)
   await client.agents.modify(agentId, { model: modelHandle });